/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System;
using System.Collections.Generic;
using System.Text;

namespace Lucene.Net.Util
{
    public sealed class ArrayUtil {

        public static int GetNextSize(int targetSize)
        {
            /* This over-allocates proportional to the list size, making room
             * for additional growth.  The over-allocation is mild, but is
             * enough to give linear-time amortized behavior over a long
             * sequence of appends() in the presence of a poorly-performing
             * system realloc().
             * The growth pattern is:  0, 4, 8, 16, 25, 35, 46, 58, 72, 88, ...
             */
            return (targetSize >> 3) + (targetSize < 9 ? 3 : 6) + targetSize;
        }

        public static int GetShrinkSize(int currentSize, int targetSize)
        {
            int newSize = GetNextSize(targetSize);
            // Only reallocate if we are "substantially" smaller.
            // This saves us from "running hot" (constantly making a
            // bit bigger then a bit smaller, over and over):
            if (newSize < currentSize / 2)
                return newSize;
            else
                return currentSize;
        }

        public static int[] Grow(int[] array, int minSize)
        {
            if (array.Length < minSize)
            {
                int[] newArray = new int[GetNextSize(minSize)];
                Array.Copy(array, 0, newArray, 0, array.Length);
                return newArray;
            }
            else
                return array;
        }

        public static int[] Grow(int[] array)
        {
            return Grow(array, 1 + array.Length);
        }

        public static int[] Shrink(int[] array, int targetSize)
        {
            int newSize = GetShrinkSize(array.Length, targetSize);
            if (newSize != array.Length)
            {
                int[] newArray = new int[newSize];
                Array.Copy(array, 0, newArray, 0, newSize);
                return newArray;
            }
            else
                return array;
        }

        public static long[] Grow(long[] array, int minSize)
        {
            if (array.Length < minSize)
            {
                long[] newArray = new long[GetNextSize(minSize)];
                Array.Copy(array, 0, newArray, 0, array.Length);
                return newArray;
            }
            else
                return array;
        }

        public static long[] Grow(long[] array)
        {
            return Grow(array, 1 + array.Length);
        }

        public static long[] Shrink(long[] array, int targetSize)
        {
            int newSize = GetShrinkSize(array.Length, targetSize);
            if (newSize != array.Length)
            {
                long[] newArray = new long[newSize];
                Array.Copy(array, 0, newArray, 0, newSize);
                return newArray;
            }
            else
                return array;
        }

        public static byte[] Grow(byte[] array, int minSize)
        {
            if (array.Length < minSize)
            {
                byte[] newArray = new byte[GetNextSize(minSize)];
                Array.Copy(array, 0, newArray, 0, array.Length);
                return newArray;
            }
            else
                return array;
        }

        public static byte[] Grow(byte[] array)
        {
            return Grow(array, 1 + array.Length);
        }

        public static byte[] Shrink(byte[] array, int targetSize)
        {
            int newSize = GetShrinkSize(array.Length, targetSize);
            if (newSize != array.Length)
            {
                byte[] newArray = new byte[newSize];
                Array.Copy(array, 0, newArray, 0, newSize);
                return newArray;
            }
            else
                return array;
        }

        /// <summary>
        /// Returns hash of chars in range start (inclusive) to end (inclusive).
        /// </summary>
        public static int HashCode(char[] array, int start, int end)
        {
            int code = 0;
            for (int i = end - 1; i >= start; i--)
                code = code * 31 + array[i];
            return code;
        }

        /// <summary>
        /// Returns hash of chars in range start (inclusive) to end (inclusive).
        /// </summary>
        public static int HashCode(byte[] array, int start, int end)
        {
            int code = 0;
            for (int i = end - 1; i >= start; i--)
                code = code * 31 + array[i];
            return code;
        }
    }
}
